171 ТЕКСТЫ ДЛЯ РЕФЕРИРОВАНИЯ ПО ВЫЧИСЛИТЕЛЬНОЙ ТЕХНИКЕ - Страница 15

Text 20. HARDWARE COMPONENTS: DISPLAYS, KEYBOARDS, PROCESSORS, AND STORAGE

INFORMATION PROCESSING WORKSTATIONS

Today equipment that once handled only word processing applications is capable of using the different types of software. The equipment on which word processing was done was called a word processor. Word processing can presently be done on equipment dedicated solely to this application, or it can be done on a general-purpose piece of equipment that uses a variety of different types of software such as spreadsheet applications software, data base software, and graphics software. A term more appropriate for this type of equipment is an information processor.

Information processor is a general term that is applied to the various computers in use today. Some of the terms commonly used to refer to information processors are word processors, office information systems, and personal computers.

Certain parts make up an information processor. The components of a personal computer have been chosen to illustrate these parts because they are representative of the parts of nearly any computer system in use today. Whatever the machine, it will have a keyboard, video display, central processing unit, storage unit, and possibly a printer.

A keyboard is the most common means of entering information and instructions into a computer (inputting); a visual display and a printer are standard means of getting information from the computer back out to the user (outputting). All computers also need the equivalent of a disk drive, a device used in running additional software and storing information.

When grouped together, these components may be called a workstation.

Nondisplay systems (Blind Terminals)

Nondisplay systems are workstations that print output (hard copy) using the same piece of equipment for inputting and outputting. For this reason, they are referred to as combination input/output terminals or 1/0 terminals. These input/output terminals do not provide the opportunity to view the entire page of material as corrections or revisions are being made. They are, therefore, called blind terminals. Only the portion of the text that is changed appears on the printed page (unless the entire text is played out on paper). Very few of the workstations in use in industry today are blind terminals.

Visual Display Terminals

An important component of a workstation is a visual display terminal (VDT). A visual display terminal is a television-like screen, often called a monitor. Although visual displays are presently found on the majority of workstations, the first word processors were nondisplay systems.

- 48 -

Workstations with a visual display terminal show the document being key-boarded (inputted) or retrieved from storage. Using a VDT makes it possible to produce a document without the use of paper. Corrections and changes made at the keyboard can be seen on the screen. When all the corrections and revisions have been made, the document is recorded on storage media and can be played back at a later time.

Advantages:

1. You see the document during its creation.

2. You can proofread, correct, and revise the document before it is printed.

3. The process is done on a screen so that no paper is used.

4. You can clearly see the correction when revising rather than striking over the change/error and waiting for a printout to see the revised copy.

5. You can keyboard the next page while the printer types the previous page.

6. Printout and key-hoarding can occur simuitaneously.

7. A proofreader can use a different VDT as a second monitor, revise if necessary, and begin the printout while the original text is still being keyboarded.

Disadvantages:

1. Display systems are more expensive than nondisplay systems because the initial "typing" shows up on a screen and not on paper. Most systems include a separate printer to create the final document.

2. Eyestrain is a factor. Considerable research has been done on these systems to determine the effect of working with VDTs.

Features of a video display screen are:

1. Number of lines presented on the screen are from 1 to 66 at a time.

2. Wraparound capability (visual width expanse).

3. The scroll-up feature of the screen allows the operator to bring lines into view  from the top or bottom of the screen.

4. Visual components are CRT, EL, gas plasma, or liquid crystal.

5. Visual characteristics are: a. Color (green on black; white on green; black on white; amber on   black). b. Nonglare screens.

Four major technologies, each with its own characteristic resolution (clarity), size, and weight are used in visual display terminals. Resolution is the number of identifiable elements on a display, often expressed in lines per inch. The identifiable items or pixels (picture elements) are the smallest elements that are visible on a display screen. The greater the number of pixels, the higher the resolution. Many graphics applications require high-resolution displays.